Evaluation of the Influence of Neighboring Radioactive Sources Placed on a Rotating Disk on the Photon Energy Spectrum

The energy spectra of numerous radioactive samples placed on a rotating disk can be measured with a single-gamma radiation detector. This technique provides also lifetime information when the same sample returns several times close to the radiation detector. However, the presence of neighboring sources may affect the primary measurement. Assuming equal activity of all sources, analytical formulas for the relative contribution of neighboring sources are developed for typical configurations of 2, 3, 4, 6, 8, 12, 16 samples on the rotating disk. The calculated values compare well to the experimental results obtained for the configuration of 16 samples. The resulting analytical formulas help to decid, whether a passive shield around the detector is needed to reduce the contribution from neighboring samples, prior to the precise Monte Carlo simulation of the experimental set-up.